Biomass Bonus Crop

Ryan Fosso surveys a 305-acre cornfield being harvested on a dry, sunny day in mid-October. The field, planted April 29, is yielding nearly 200 bu./acre — better than Fosso expected after 2008's wet, slow start.

The central Minnesota farmer has another cause for satisfaction, too. He is paying for the cost of combining this field with corn cobs.

The cobs are destined for a newly commissioned biomass burner at the Chippewa Valley Ethanol Company (CVEC) in Benson, MN. Chippewa Valley plans to gasify cobs to power the 46-million-gallon/year corn refinery. “CVEC is providing a market for cobs, and we, as shareholders, are stepping up to supply it,” says Fosso, who raises 5,000 acres of corn, soybeans and wheat with his brother Lonnie near Pennock, MN.

As new biomass markets emerge, the humble corn cob could become an important bonus crop for Midwest farmers. Cobs are “a valuable resource that we haven't been using,” says Gene Fynboh, a Brandon, MN, farmer and longtime leader of the Minnesota Corn Research & Promotion Council.

The Fosso brothers will earn about $25/acre from their cobs, says Fynboh, a CVEC board member and the plant's biomass coordinator. That's roughly $30/ton. The ethanol plant arranged for custom combining and cob collection, and is paying the cost of trucking the cobs to the gasifier. Ryan figures that the extra cob revenue will recoup his grain harvest costs.

The Fossos are also shareholders in the 980-member ethanol cooperative — one of the first in the country to replace natural gas with biomass power. “We've got an ownership stake in the company,” Ryan says. “If CVEC takes our cobs and reduces its energy costs, we'll see that on the back side. I hope this can be a first step toward producing our own energy.”

By 2009, the ethanol maker expects biomass gasification to supplant 90% of its natural gas use. Currently, CVEC is fueling its biomass gasifier with wood chips; but in time it will run mainly on corn cobs, Fynboh says. “We buy corn for the plant from 112,000 acres. Those same acres could supply 75% of the energy needs of the plant.”

CORN STOVER — the stalks, leaves and cobs — is often touted as the biomass feedstock of the future. But cobs alone “have a lot of advantages,” says CVEC Chief Executive Bill Lee, a chemical engineer and past president of the Renewable Fuels Association.

Compact, naturally dense cobs have a higher btu value than corn stover and generate about a third of the ash when combusted, Lee says. Cobs can be stored in open piles, are easy to transport and can be handled with standard wood-chip-handling equipment, he says. Powering the ethanol plant with corn cobs will also reduce CVEC's exposure to volatile natural gas prices, says Andrew Zurn, CVEC plant engineer. And cobs could cut the plant's energy costs by one-fourth or more, he says.

In the field, cobs — which make up about 8-20% of corn residue — decompose slowly and provide fewer nutrients and erosion control than the leaves and stalks. “Collecting just the cobs is definitely more environmentally friendly than taking most of the residue,” says Jeff Coulter, a University of Minnesota Extension corn agronomist. He discourages removing corn residue except in high-yielding, continuous-corn systems. By contrast, “It's reasonable to take off all the cobs even in a corn-soybean rotation,” he says.

Another plus for cobs: collection doesn't require an additional time-consuming operation in the fall, says Riley Maanum, research and project manager for the Minnesota Corn Growers Association, which helped sponsor cob harvesting demonstrations in central Minnesota this fall.

Lee adds: “Cobs produce very little value in the field, so why not use them?” Before long, he predicts, “a lot of cobs could start to find markets.”

This fall, Lee's company bought 5,000 acres of cobs to test-burn in its new flexible-fuel gasifier. Farmers flocked to fill the need, Fynboh says, offering 30,000 acres for harvest. Eventually, the plant expects to buy more than 100,000 acres of cobs a year.

South Dakota-based Poet, the country's largest ethanol producer, will roll out a pilot cellulosic ethanol plant in Scotland, SD, this year, which will run on corn cobs. As early as 2011, the company plans to produce 25 million gallons of ethanol from cobs at a biorefinery in Emmetsburg, IA.

OTHER ENERGY AND industrial uses are emerging, too. Cobs are similar to wood in btu value, and can be blended with coal at coal-fired power plants, says Jay Van Roekel, segment manager for Vermeer Corporation of Pella, IA, which is testing a prototype corn cob harvester. “We're very optimistic about the prospects for cobs,” he says. “The markets are here. We don't need to wait for cellulosic ethanol.”

Anticipating corn cob demand, many farm equipment companies are now developing and testing cob-harvesting machines. In the past, cob milling hasn't been a big enough sector to spur much interest from implement makers, Theis says. “But gasification and cellulosic ethanol could increase demand for cob tonnage and help drive technological innovation.”

Two prototype cob harvesters roll over Lonnie and Ryan Fosso's cornfield, collecting both grain and cobs in a single pass. The Vermeer CCX770 Cob Harvester, a wagon-style cob collector, is pulled behind the combine. A fan system sorts the cobs from the leaves and stalks and blows the cobs into a bin. A hydraulic lift, controlled from the combine cab, raises the bin about 14 ft. high to dump around 7,000 lbs. of cobs.

Another prototype, the Ceres Residue Recovery System, is mounted on a combine. Corn cobs are sifted out of the residue in a CleanBoot at the back of the combine and thrown up into the TopTank, a bin that rides piggyback on the combine grain hopper and folds down for moving from field to field. The CleanBoot can also be used alone, with the air chute turned around to fill a pulled cart.

The two CaseIH combines are clipping along at near-normal speeds, Ryan Fosso observes, taking a break from hauling corn to town. “I don't think harvesting cobs would slow us down much.”

COB CRITERIA

Cob traits may soon join the list of attributes you consider when you choose your corn hybrids.

Cob size, density, yield, field drydown and storage characteristics vary a lot, says Mike Reese, director of renewable energy at the University of Minnesota West Central Research and Outreach Center (WCROC) in Morris, MN. As biomass energy markets develop, these differences will matter, says Reese, who is leading research on biomass feedstocks and gasification.

WCROC is collecting data on 5,000 acres of corn cobs that will be burned in new biomass gasifiers at the Chippewa Valley Ethanol Company in Benson, MN, and the University of Minnesota, Morris.

Moisture is one of the most important variables for biomass energy feedstocks, Reese says. The cobs harvested this fall ranged from 31.2% to 53.2% moisture, he says. Grain moisture ranged from 19.9% to 33%. Desirable cob moisture for gasification is 25% or less.

The cobs will be stored in open piles this winter, and are expected to “dry some in storage,” Reese says. Some of the piles have also been ventilated with 12-in. corrugated drain tile. Researchers will be monitoring temperature, moisture and tonnage losses in the cob piles.

Pounds of cobs per acre is another key variable. Cobs make up 8-20% of corn residue, Reese says. A 200-bu./acre corn crop is expected to yield 1,000-2,000 lbs. of cobs/acre. However, commercial cob harvesters report extreme variability in cob yields, he says.